In the magnetic data recording arts, the disc-shaped medium is now perhaps the most prominent. Many of these are made to be detachable from the drive mechanism. Because of the necessity to keep them free of contamination, the rigid type of detachable disc cartridge is now invariably totally enclosed in a housing when not mounted on a drive. To provide access to the disc surfaces for the magnetic data transducers, the housings for detachable discs again typically have a detachable dust shield or cover which closes, while this cartridge is unmounted on a drive, the ports through which the disc and its spindle are accessed during operation. One particular type of cover is magnetically attached to a ferrous portion of the hub assembly which carries the discs and which is magnetically attached to the spindle of the drive for rotation of the discs. Magnets set near the center of the cover clamp it to the hub and securely press its periphery against a mating surface on the housing to exclude contamination. The drive spindle is similarly attached with magnets to the hub when the cartridge is mounted in a drive.
In these designs, it is typical to employ a so-called double-acting handle which in the first place may be used to carry the cartridge by simply lifting it. If a slide on the handle is manually actuated before the handle is lifted, an internal mechanism operates to break the magnetic attraction between the hub and the cover or the spindle greatly simplifying detaching the hub from either. Such double-acting handles have been available for several years. They are typically now manufactured with an internal metal mechanism to provide the selectable functions and necessary leverage for detaching the cover. Although metal is perfectly satisfactory from a functional standpoint, the use of plastic for this double-acting mechanism is attractive because costs can be substantially lowered through its use. Because of the lesser strength and stiffness of plastic however, it is not possible to directly duplicate the design of the metal mechanism now in use, in plastic. Accordingly, it is necessary to change the internal double-acting mechanism of the handle when it is made from plastic. U.S. Pat. No. 3,635,608 discloses the internal mechanism of the prior art handle as embodied in metal. The solution we disclose below is the same in both function and operation but employs different internal design to permit the internal mechanism to be made from plastic.